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<pre><span class="sourceLineNo">001</span><a name="line.1"></a>
<span class="sourceLineNo">002</span>/*<a name="line.2"></a>
<span class="sourceLineNo">003</span> * Copyright (C) 2011 Archie L. Cobbs. All rights reserved.<a name="line.3"></a>
<span class="sourceLineNo">004</span> *<a name="line.4"></a>
<span class="sourceLineNo">005</span> * $Id: TimedWait.html 852 2014-03-19 16:40:39Z archie.cobbs $<a name="line.5"></a>
<span class="sourceLineNo">006</span> */<a name="line.6"></a>
<span class="sourceLineNo">007</span><a name="line.7"></a>
<span class="sourceLineNo">008</span>package org.dellroad.stuff.java;<a name="line.8"></a>
<span class="sourceLineNo">009</span><a name="line.9"></a>
<span class="sourceLineNo">010</span>/**<a name="line.10"></a>
<span class="sourceLineNo">011</span> * Utility class for performing timed waits on objects.<a name="line.11"></a>
<span class="sourceLineNo">012</span> *<a name="line.12"></a>
<span class="sourceLineNo">013</span> * @see Object#wait<a name="line.13"></a>
<span class="sourceLineNo">014</span> */<a name="line.14"></a>
<span class="sourceLineNo">015</span>public final class TimedWait {<a name="line.15"></a>
<span class="sourceLineNo">016</span><a name="line.16"></a>
<span class="sourceLineNo">017</span>    private static final long MAX_WAIT_MILLISECONDS = 0x7fffffffffffffffL / 1000000L;<a name="line.17"></a>
<span class="sourceLineNo">018</span><a name="line.18"></a>
<span class="sourceLineNo">019</span>    private TimedWait() {<a name="line.19"></a>
<span class="sourceLineNo">020</span>    }<a name="line.20"></a>
<span class="sourceLineNo">021</span><a name="line.21"></a>
<span class="sourceLineNo">022</span>    /**<a name="line.22"></a>
<span class="sourceLineNo">023</span>     * Wait (using {@link Object#wait(long) Object.wait()}) up to a given time limit for some predicate to become true.<a name="line.23"></a>
<span class="sourceLineNo">024</span>     * This method correctly handles {@link Object#wait spurious wakeups}, restarting the wait loop as necessary.<a name="line.24"></a>
<span class="sourceLineNo">025</span>     *<a name="line.25"></a>
<span class="sourceLineNo">026</span>     * &lt;p&gt;<a name="line.26"></a>
<span class="sourceLineNo">027</span>     * This method assumes that {@code obj} will be notified whent the predicate becomes true and that the current thread<a name="line.27"></a>
<span class="sourceLineNo">028</span>     * is already synchronized on {@code obj}. It also guarantees that upon return, {@code obj} will have remained<a name="line.28"></a>
<span class="sourceLineNo">029</span>     * continuously locked since the most recent invocation of {@link Predicate#test predicate.test()}, so that any<a name="line.29"></a>
<span class="sourceLineNo">030</span>     * derived state computed therein will still be valid.<a name="line.30"></a>
<span class="sourceLineNo">031</span>     * &lt;/p&gt;<a name="line.31"></a>
<span class="sourceLineNo">032</span>     *<a name="line.32"></a>
<span class="sourceLineNo">033</span>     * &lt;p&gt;<a name="line.33"></a>
<span class="sourceLineNo">034</span>     * This method uses {@link System#nanoTime} instead of {@link System#currentTimeMillis} and so is immune to<a name="line.34"></a>
<span class="sourceLineNo">035</span>     * adjustments in clock time.<a name="line.35"></a>
<span class="sourceLineNo">036</span>     * &lt;/p&gt;<a name="line.36"></a>
<span class="sourceLineNo">037</span>     *<a name="line.37"></a>
<span class="sourceLineNo">038</span>     * @param obj       object to sleep on; must already be locked<a name="line.38"></a>
<span class="sourceLineNo">039</span>     * @param timeout   wait timeout in milliseconds, or zero for an infinite wait<a name="line.39"></a>
<span class="sourceLineNo">040</span>     * @param predicate predicate to test<a name="line.40"></a>
<span class="sourceLineNo">041</span>     * @return true if the predicate became true before the timeout, false if the timeout expired<a name="line.41"></a>
<span class="sourceLineNo">042</span>     * @throws IllegalArgumentException     if {@code timeout} is negative<a name="line.42"></a>
<span class="sourceLineNo">043</span>     * @throws IllegalMonitorStateException if {@code obj} is not already locked<a name="line.43"></a>
<span class="sourceLineNo">044</span>     * @throws InterruptedException         if the current thread is interrupted<a name="line.44"></a>
<span class="sourceLineNo">045</span>     */<a name="line.45"></a>
<span class="sourceLineNo">046</span>    public static boolean wait(Object obj, long timeout, final Predicate predicate) throws InterruptedException {<a name="line.46"></a>
<span class="sourceLineNo">047</span><a name="line.47"></a>
<span class="sourceLineNo">048</span>        // Sanity check timeout value<a name="line.48"></a>
<span class="sourceLineNo">049</span>        if (timeout &lt; 0)<a name="line.49"></a>
<span class="sourceLineNo">050</span>            throw new IllegalArgumentException("timeout &lt; 0");<a name="line.50"></a>
<span class="sourceLineNo">051</span><a name="line.51"></a>
<span class="sourceLineNo">052</span>        // Record start time (only if there's a timeout)<a name="line.52"></a>
<span class="sourceLineNo">053</span>        long startTime = timeout &gt; 0 ? System.nanoTime() : 0;<a name="line.53"></a>
<span class="sourceLineNo">054</span><a name="line.54"></a>
<span class="sourceLineNo">055</span>        // Loop waiting for predicate<a name="line.55"></a>
<span class="sourceLineNo">056</span>        while (!predicate.test()) {<a name="line.56"></a>
<span class="sourceLineNo">057</span><a name="line.57"></a>
<span class="sourceLineNo">058</span>            // Did the timeout expire?<a name="line.58"></a>
<span class="sourceLineNo">059</span>            if (timeout &lt; 0)<a name="line.59"></a>
<span class="sourceLineNo">060</span>                return false;<a name="line.60"></a>
<span class="sourceLineNo">061</span><a name="line.61"></a>
<span class="sourceLineNo">062</span>            // Wait for remaining timeout to be woken up, but not more than 292 years :)<a name="line.62"></a>
<span class="sourceLineNo">063</span>            obj.wait(Math.min(timeout, MAX_WAIT_MILLISECONDS));<a name="line.63"></a>
<span class="sourceLineNo">064</span><a name="line.64"></a>
<span class="sourceLineNo">065</span>            // If there's a timeout, subtract the time we just waited (rounding to the nearest millisecond)<a name="line.65"></a>
<span class="sourceLineNo">066</span>            if (timeout &gt; 0) {<a name="line.66"></a>
<span class="sourceLineNo">067</span>                long stopTime = System.nanoTime();<a name="line.67"></a>
<span class="sourceLineNo">068</span>                timeout -= (stopTime - startTime + 500000L) / 1000000L;<a name="line.68"></a>
<span class="sourceLineNo">069</span>                if (timeout == 0)               // don't convert the last millisecond into an infinite wait<a name="line.69"></a>
<span class="sourceLineNo">070</span>                    timeout = -1;<a name="line.70"></a>
<span class="sourceLineNo">071</span>                startTime = stopTime;<a name="line.71"></a>
<span class="sourceLineNo">072</span>            }<a name="line.72"></a>
<span class="sourceLineNo">073</span>        }<a name="line.73"></a>
<span class="sourceLineNo">074</span><a name="line.74"></a>
<span class="sourceLineNo">075</span>        // Predicate was true<a name="line.75"></a>
<span class="sourceLineNo">076</span>        return true;<a name="line.76"></a>
<span class="sourceLineNo">077</span>    }<a name="line.77"></a>
<span class="sourceLineNo">078</span>}<a name="line.78"></a>
<span class="sourceLineNo">079</span><a name="line.79"></a>




























































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